Horigan
Senior Chief Petty Officer
- Joined
- Jun 12, 2016
- Messages
- 673
I have a short in my ignition circuit on my '95 joint venture (Volvo/OMC) Ford 5.0 EFI engine that I'm about to start troubleshooting. The 20A circuit breaker for the ignition system is blown.
While cruising at 3000 rpm the motor just shut off, no sputter or any hesitation prior. Right at shutdown I noticed the tachometer slowly started rising from 3000 to fully pegged. I was able to restart the engine, but it abruptly shutdown after ~five seconds of idling. Found nothing unusual in the engine compartment. Gave the engine a rest while we swam in the lake. Half an hour later the engine restarted and we started heading back to the dock at 3000 rpm and the engine shutdown again abruptly. Tried, but failed, to restart and noted a mild electrical overheat smell. Now there is no power to the displayed gauges or Floscan accessory fuel meter. Found the ignition fuse blown and got towed back to the dock.
I suspect a short to ground in the ignition circuit (hopefully still present). There are several accessories tied to the ignition switch that are in the circuit (Floscan, Halon fire suppression, etc). My plan is to hopefully find the short still present and determine if it's in the ignition wiring or accessory wiring.
Question: Does the tachometer behavior during the first shutdown (slow rise to fully pegged) provide a clue that the issue is in the ignition wiring or where to look?
Potentially related info: Just prior to this I resolved an issue where corrosion in the oil pressure switch connection caused the engine to drop into SLOW mode (RPMs limited to 2600). I moved the engine harness wires around while troubleshooting this. Also, the tachometer was reading a little high compared to the digital Floscan reading and I cycled the cylinder count selector on the back of the tach, which seemed to address the issue.
Oh the joys of a 29 year old boat.
While cruising at 3000 rpm the motor just shut off, no sputter or any hesitation prior. Right at shutdown I noticed the tachometer slowly started rising from 3000 to fully pegged. I was able to restart the engine, but it abruptly shutdown after ~five seconds of idling. Found nothing unusual in the engine compartment. Gave the engine a rest while we swam in the lake. Half an hour later the engine restarted and we started heading back to the dock at 3000 rpm and the engine shutdown again abruptly. Tried, but failed, to restart and noted a mild electrical overheat smell. Now there is no power to the displayed gauges or Floscan accessory fuel meter. Found the ignition fuse blown and got towed back to the dock.
I suspect a short to ground in the ignition circuit (hopefully still present). There are several accessories tied to the ignition switch that are in the circuit (Floscan, Halon fire suppression, etc). My plan is to hopefully find the short still present and determine if it's in the ignition wiring or accessory wiring.
Question: Does the tachometer behavior during the first shutdown (slow rise to fully pegged) provide a clue that the issue is in the ignition wiring or where to look?
Potentially related info: Just prior to this I resolved an issue where corrosion in the oil pressure switch connection caused the engine to drop into SLOW mode (RPMs limited to 2600). I moved the engine harness wires around while troubleshooting this. Also, the tachometer was reading a little high compared to the digital Floscan reading and I cycled the cylinder count selector on the back of the tach, which seemed to address the issue.
Oh the joys of a 29 year old boat.
